Carbon monoxide remains a significant cause of human fatality because of its colorless and odorless characteristics. The human body has generally a low tolerance for carbon monoxide gas since a concentration of approximately 0.05% over an extended period of time or 1% for a few minutes could prove to be a fatal dosage for humans. Moreover, even a minor amount of carbon monoxide can be detrimental to human health. For example, when 50 parts per million of carbon monoxide are present in air, it may provide an environment that would be impossible to work in for more than 8 hours, while 200 parts per million of carbon monoxide present in the air could cause headaches within 3 or 4 hours. The combination of high toxicity along with the colorless and odorless characteristics of carbon monoxide makes it an extremely lethal gas since its presence in the atmosphere may not be detected by a human before it causes permanent damage.
Generally at the start of a fire, all the combustible substances contain carbon and in the initial stage of the fire, carbon monoxide is generally always present. In the initial stage of a fire, combustion is incomplete and carbon monoxide is generally present since there is usually insufficient heat for complete combustion. Thus the detection of carbon monoxide at the initial stage of a fire, could result in quick notification to a person in the area which could result in the saving of lives and the minimizing of property loss.
Carbon monoxide can be present in dangerous quantities in a wide variety of different environments such as homes, automobiles, aircraft, submarines, coal mines and the like. The serious threat posed by carbon monoxide, as evidenced by the appreciable annual fatalities due to exposure to an excessive amount of carbon monoxide, has resulted in the development of numerous quantitative procedures for detecting the presence and concentration of carbon monoxide in closed environments. A common type of analytical process would involve the oxidizing of the carbon monoxide to form carbon dioxide with the release heat providing a quantitative indication of the amount of carbon dioxide present. However, such devices required for this detection means are generally quite complex and expensive.
U.S. Pat. No. 2,487,077 discloses a carbon monoxide indicating composition, process and detection device. The composition consists essentially of a body of purified silica gel freed of substances oxidizable by hot concentrated nitric acid and having combined therein essentially dry residues of impregnation with a solution of palladium sulfate, sulfuric acid and ammonium molybdate, in proportions by weight of about 500 to 1600 parts gel, 5 to 50 parts acid containing about 1 part palladium, and about 10 to 60 parts molybdate. The composition is free of chloride ion.
Canadian Pat. No. 477,288 discloses a granular reagent adapted to undergo a color change in the presence of carbon monoxide consisting of a partly dehydrated granular product prepared by impregnating silica gel with a salt selected from the group consisting of alkali molybdates and tungstates, with a mineral acid, and with palladous halide.
U.S. Pat. No. 3,245,917 discloses a self-regenerating reagent for detecting the presence of carbon monoxide at a relative humidity of at least 20%, consisting essentially of a carrier of silica gel having adsorbed thereon palladium chloride and a regenerating amount of hydrochloric acid.
U.S. Pat. No. 4,043,934 discloses a self-regenerating reagent which, on contact with a reducing gas, oxidizes the gas and is reduced from an oxidized state to a reduced state. The reagent comprises a mixture of a palladium salt, a compound which includes a complex ion of a metal selected from the group consisting of molybdenum, tungsten and vanadium, and a salt of a metal selected from the group consisting of copper, nickel and iron, and a hydrophilic carrier for the mixture. Silica gel is among the possible carriers disclosed and carbon monoxide detection is one of the uses disclosed for the composition.
It is the object of the present invention to provide a novel material for detecting the presence of carbon monoxide.
It is another object of the present invention to provide a novel sensor having a high sensitivity to carbon monoxide.
It is another object of the present invention to provide a novel sensor that changes color upon the detection of carbon monoxide.
It is another object of the present invention to provide a carbon monoxide sensor material of a solid state derivative of Ni(TBC) which upon detecting the presence of carbon monoxide changes color.
It is another object of the present invention to provide a novel carbon monoxide sensor which retains its sensitivity over an appreciable period of time without substantial maintenance cost and which is cost effective to produce.
The above and further objects and advantages of this invention will become apparent upon consideration of the following description thereof.